Driver circuit for speeding response of remotely controlled apparatus

ABSTRACT

A fluid motor system controlled by electrical signals originating at a remote location has driver circuits, for energizing motor control valve solenoids in response to signals, with means for assuring fast termination of motor operation upon termination of a control signal. Upon termination of a signal causing motor operation in one direction, the circuit momentarily actuates the motor in the opposite direction. Capacitive means in the driver circuit undergoes a change of charge condition while a control signal is received and thereafter produces a momentary reverse operation signal while reverting to the original charge condition.

United States Patent Coleman et al.

[54] DRIVER CIRCUIT FOR SPEEDING RESPONSE OF REMOTELY CONTROLLEDAPPARATUS Donald F. Coleman, Dunlap; Joe E. Fuzzell, Peoria, both of111.

Assignee: Caterpillar Tractor Co., Peoria, 111.

Filed: Nov. 2, 1970 8 Appl. No.: 85,853

Inventors:

US. Cl. ..307/254, 91/459, 307/270, 318/61 1 Int. Cl. ..G05b 5/01 Fieldof Search ..307/255, 270, 254; 318/611, 318/672-674; 91/459 [5 6]References Cited UNITED STATES PATENTS [is] 3,694,671 51 Sept. 26,1972

Wanlass ..307/255 Ringoen ..318/672 Primary Examiner-James W. LawrenceAssistant Examiner-Harold A. Dixon Attorney-Fryer, Tjensvold, Feix,Phillips & Lempio [5 7] ABSTRACT 3,281,630 10/1966 Liang ..307/2549Claims,2Drawing Figures 43 2 53 5e 3 A 44 3e 52 57' 48 3 7 EXTEND 54 4738 FLfUlD 516N41- SOURCE Y2]? 39? TRANSMITTER RECEIVER 29$ E A 4r 42 426 v D" I I are" 33 49 46 2 PATENTEDsms I972 SHEET 1 [IF 2 mUmDOm QSJLINVENTORS DONALD F. COLEMAN JOE E. FUZZELL wUmDOW am si A'I'TORNEYSSHEET 2 BF 2 wumzom 05 INVENTORS DONALD F. COLEMAN JOE E. FUZZELL BY v y7% Hi 1 9 ATTORNEYS BACKGROUND OF THE INVENTION This inventionrelates toelectrical systems for controlling apparatus in response to signalsreceived from a remote location and more particularly to a drivercircuit for actuating and deactuating an electrically controlled devicein response to such signals.

Certain forms of mechanical apparatus having motors which are controlleddirectly or indirectly by electrical signals may exhibit a degree ofoperational inertia in that the motor may not stop immediately upontermination of the control signal which initiated the motor operation.One example of apparatus of this kind is-disclosed in copendingapplication Ser. No. 822,368 of Joe E. Fuzzell filed May 7, 1969,entitled Remote Control System for Load Manipulating Vehicles andassigned to the assignee of the present application. This copendingapplication discloses a loader vehicle, of the form used formanipulating earth or other materials, which may be operated throughradio signals originating at a control box some distance away from thevehicle. This is accomplished by providing extensible and contractiblefluid cylinders on the vehicle in the linkages which connect theoperators conventional control levers with the hydraulicvalving operatedthrough such levers. By fixing the operatorscontrol levers in positionand utilizing solenoid operated control valves to extend or contract thefluid cylinders in response to the signals from the remote location,remote control of all the basic vehicle functions is realized.

To deactivate the vehicle mechanism controlled by the cylinders when aremote signal is terminated springs are providedto restore the cylindersto the appropriate degree of extension for stopping the controlledmechanism.

Tln the absence-of corrective measures, a significant period of time maybe required for the fluid cylinder to be spring restored to the positionat which the associated vehicle mechanism is inactivated. This producesan undesirable overshoot of the controlled mechanism. Efficient use ofthe vehicle is made difficult and in some situations a risk of damage orpersonnel injury may be present; I

An experienced observer operating the vehicle from a distance may learnto make proper allowances in the timing of his actuation of the controlswitches or the like but at best this greatly complicates remoteoperation of the vehicle and imposes an undesirable burden on the remoteoperator. Essentially similar problems are encountered in other forms ofremotely operated apparatus.

SUMMARY OF THE INVENTION This invention is a circuit for actuating anddeactuating mechanism in response to electrical signals wherein themechanism is stopped extremely rapidly and reliably in response to aterminating signal. A capacitive element in the circuit is arranged tochange charge state during receipt of a signal which initiates operationof the controlled apparatus. Upon termination of the actuating signalthe capacitive element reverts to the original charge condition therebymomentarily generating a control signal of the form which tends toproduce an oppositely directed operation of the controlled apparatus.The. reverse control signal has a duration sufficient to rapidly stopthe controlled apparatus in its original motion but insufficient toproduce an actual reverse movement thereof. Accordingly, the controlledapparatus responds much more rapidly and reliably to a motionterminating control signal.

Accordingly, it is an object of this invention to provide for fastresponse of remotely controlled apparatus to control signals. g

The invention, together with further objects and advantages thereof,will best be understood by reference to the following description ofpreferred embodiments taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a schematic diagram of an electrically controlled fluid motorand an electrical controlcircuit in accordance with the presentinvention which responds to radio signals from a remote location; and

FIG. 2 is a schematic diagram of a second embodiment of the inventionparticularly adapted for controlling a fluid motor with electricalsignals transmitted through an umbilical cord containing electricalconductors.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now tothe drawing andmore particularly to FIG. 1 thereof, there is shown a hydraulic motorsystem 11 typical of mechanisms which it may be desired to controlthrough electrical signals originating at a remote location. The system1 l of this example includes a fluid motor 12 which is a double actinghydraulic cylinder that may be caused to extend or retract or remain ata given position by pivoting an actuator lever 14 of a control valve 13.

Actuator lever 14 has a center position at which both the rod and headends of motor 12 are blocked and the motor is held in a stationaryposition. Clockwisemovement of lever 14 as viewed in FIG. 1 transmitspressurized fluid from a suitable source 16 to the head end of the motorwhile venting the rod end to a drain l7. Counterclockwise movement ofthe actuator lever 14 pressurizes the rod end of the motor 12 whileventing the head end to cause contraction.

The system 11 as herein shown is a means for raising and lowering thebucket of a loader vehicle of the form described in the hereinbeforeidentified copending application Ser. No. 822,368 wherein the valve 13may be manually controlled by an operator through a control lever 18connected to the actuator lever 14 through linkage 19. As described tothis point, the system 11 is essentially conventional and provides ameans whereby the motor 12 is controlled by an operator situated on thevehicle.

As set forth in more detail in the above identified copendingapplication, the system 11 also provides for optional control of themotor 12, as well as other components of the vehicle, through radiosignals originating at a remote transmitter 21. To realize this optionalmode of control, the operators control lever 18 is immobilized at thecenter or hold position by transpiercing a suitable pin 22 through thecontrol lever and into adjacent stationary structure. Part of thelinkage 19 is Hold position at which motor 12 is defined by a fluidcylinder 23 having a head end connected to the control lever and havingextensible and contractible rod 24 connected to the actuator lever 14 ofvalve 13. A pair of compression springs 26 within cylinder 23 act on thepiston therein to tend to main: tain the cylinder in a state ofintermediate extension. Thus, when the operators control lever 18 isimmobilized as previously described, springs 26 urge the control valveactuator lever 14 towards the intermediate or stopped.

Owing to the presence of the centering springs 26, cylinder 23 functionseffectively as a rigid linkage between control lever 18 and valveactuator lever 14 when the system is operated in v the conventionalmanner by an operator who is present on the vehicle. However, with theoperators control lever 18 immobilized, extension of cylinder 23 shiftsvalve lever 14 to a position causing extension of motor 12 whilecontraction of cylinder 23 shifts the valve to cause contraction of themotor. Control of cylinder 23 for this purpose in response to signalsfrom the radio transmitter2l is realized through a pair of solenoidoperated valves 27 and 28.

Solenoid valve 27 has an unenergized position at which the head end ofcylinder23 is vented to a drain 29 and an energized position at which afluid source 31 is coupled to the head end of the cylinder. Similarlysolenoid valve 28 has an unenergized position venting the rod end ofcylinder 23 to drain 29 and anenergized position connecting fluid source31 with the rod end of the cylinder. Fluid source 31 is shown separatefrom source 16 in this example of the invention as there are oftenadvantages to using lower pressure fluid for operating cylinder 23 asopposed to motor 12.

Accordingly, with the operators control lever 18 immobilized, motor 12may be caused to extend by energizing the solenoid 27' of valve 27 andmay be caused to contract by energizing the solenoid 28' of valve 28.Upon de-energizing of either solenoid, both ends of cylinder 23 arecommunicated to drain 29 arid springs 26 act to center the actuatorlever 14 to stop movement of motor 12. In the absence of correctivemeasures, this stopping of motor 12 in responseto de-energizationof asolenoid 27 or 28 may involve an undesirable time delay in that asizable quantity of fluid must flow from one end or the other ofcylinder 23 in response to the pressure of springs 26 before actuatorlever 14 is fully returned to' the center or Hold position. Thus, thesystem 11 may not respond instantaneously to the termination of acontrol signal from transmitter 21 and an undesirableovershoot of themotor 12 may occur. This is avoided in the present invention by a drivercircuit 32 which respondsto termination of a signal from transmitter 21not only by de-energizing the particular solenoid 27' or 28' which hasbeen energized but also by momentarily energizing the oppositesolenoidto accelerate the centering effect of springs 26 in cylinder 23.

Driver circuit 32 operates from a suitable DC power supply 33 which maybe the vehicle battery in this particular example of the invention and.has a positive power conductor 34 coupled to a terminal of solenoid 27through the emitter collector circuit of a power transistor 36 andconnected to a terminal of solenoid 28' through the emitter collectorcircuit of a similar transistor 36'. The other terminal of each solenoid27 and 28' is grounded and the solenoids 27 and 28' have diodes 37 and37' connected respectively thereacross through resistors 38 and 38'respectively to protect against inverted transient voltage spikes. Thuseither solenoid 27 of 28' may be energized by biasing the associatedtransistor 36 or 36' to conduction.

Suitable detailed constructions for the transmitter 21 and the receiver39 are set forth in the hereinbefore identified copending applicationSer. "No. 822,368. Transmitter 21 is provided with a series of manuallyoperable switches 41 and 41' which may be depressed by a remote operatorto initiate extension and contraction respectively of the fluid motor12. Depression of switch 41 initiates a radio signal which in turninitiates a positive DC electrical signal on an Extend signal conductor42 of receiver 39 while depression of switch 41 initiates a similarsignal on a Contract signal conductor 42' at the receiver. Manyadditional control signal channels may actually be present at thetransmitter 21 and receiver 39 to control a variety of functions, thepresent description being confined to the two channels for initiatingextension or contraction of motor 12 in asmuch as essentially similarcircuitry may be utilized to control any number of additional motors 12or the like.

Considering now the circuitry which renders transistor 36 and 36conductive in the'presence of a signal on conductors 42 or 42respectively, the base of each transistor isconnected to the positiveside of battery'33 through the emitter collector circuit of anassociated one of two driver transistors 43 and 43' respectively. Thebase of each transistor 36 and 36' is also connected to the emitter sidethereof through the associated one of the previously described resistors38 and thus each transistor 36 or 36' is held non-conductive until suchtime as the associated driver transistor 43 or 43' becomesconductive.Conduction through either of the driver transistors 43 or 43 establishesa voltage drop across the associated resistor 38 biasing the transistor36 or 36' into conduction.

Driver transistors 43 and 43' are held non-conductive in the absence ofsignals on conductors 42 and 42' by an associated one of pair of thirdtransistors 44 and 44'. The collectors of transistors 44 arid'44' areconnected to positive power supply conductor 34 through I resistors 46and 46' respectively and the emittersof the two third-transistors aregrounded through resistors 47 and 47 respectively. The collectors oftransistors 44 and 44 also connect to the basesof driver transistors 43and 43 respectively through additional resistors 48 and 48. Resistors 47and 47' have relatively small values in comparison with resistors 46 and46' and therefore a potential close to ground is provided to the base oftransistors 43 and 43', holding the transistors non-conductive, as longas the third transistors 44 and 44' are conductive. The thirdtransistors 44 and 44' are held conductive, in the absence of inputsignals on conductors .42 and 42', through a base connection to positivebattery through resistors 49 and 49' respectively and a base connectionto ground'through resistors 51 and 51' respectively. Resistors 49'and 51and resistors 49 and 51' thus constitute voltage dividers normallybiasing the bases of third transistors '44 and 44' respectively toestablish conduction therethrough.

. through a diode57 'and'resistor'58with'thebase of transistor 43' whilecontract signal conductor 42 similarly connects with 'the base oftransistor -43 through a diode 57 and resistor-58.

In operation, with no signals on conductors-42 and 42', powertransistors 36 and 36' are non-conductive for the reasons hereinbeforedescribed and thus solenoids 27' and 28' are unenergized and the motorcontrol valve lever 14 is therefore in the centered. positionimmobilizing the motor 12. Under this condition capacitors56 and 56'have a small positive charge due to the connection of the capacitors tothe voltage dividers defined by resistors 49 and 51 and 49' and 51'.When, for example an Extend signal is received on signal conductor 42the signal is transmitted through diode 57 to the base of transistor 43'cau'sing transistor 43' to conduct andthereby provide base drive topower transistor 36'.. Power transistor 36' saturates and closes thecircuit from the positive side of battery 33 to ground through solenoid28' thereby energizing the solenoid and operating valve 28. Valve 28then applies fluid pressure to the rod end of cylinder 23 which retractsto pull control valve 13 actuator lever 14 clockwise as viewed in.FIG. 1. Fluid from source 16 is thereby supplied to the head end ofmotor 12 causing the motor to extend.

During the period that the Extend signal is present on signal conductor42, the chargeon capacitor 56 reverses polarity and rises to a higherlevel than was formerly the case.

When the Extend signal on conductor 42 is terminated, base bias throughdiode 57 and resistor 58 is removed from transistor 43'. Transistor 43'turns off thereby removing base bias frompower transistor 36' andopening the circuit between battery 33 and solenoid 28. Valve 28 thenreverts to the de-energized position at which the rod end of cylinder 23is opened to drain 29. Springs 26 are thus enabled to begin centeringthe piston of cylinder 23 to restore control valve 13 actuator lever 14to the intermediate position to immobilize motor 12.

As immobilization of motor 12 in this manner requires that a finitevolume of fluid be expelled from cylinder 23 through the actions ofsprings 26, some sizable delay would occur, in the absence of correctivemeasures, before control valve 13 is fully restored to the Holdposition. Considering now the means by which the present inventionreduces this delay to an in significant time period, the termination ofthe extend signal on conductor 42 acts, in addition to the effectsdescribed above, to: enable capacitor 56 to begin to discharge at a ratedetermined by the values of the resistors 52, 53, 54and 49 as well asthe value of the capacitor itself. As the capacitor 56 is discharging,the potential at the base of transistor 44 decreases shutting offtransistor boss of conduction through transistor 44 causes a positivevoltage riserat the base of transistor 43 whichbecomes'conductive andprovidesbase drive to power transistor 36 which becomes conductive inturn energizing the other solenoid 27. Thisenergizing ofsolenoi'd27' ismomentary in that the circuit reverts to the original condition whencapacitor 56 is restored to the original condition.

The brief energizing of-- solenoid 27 following termination ofthe Extendsignal operates valve 27 to momentarily direct high'pressure fluid tothe rod end of cylinder '23 thereby acceleratingthe action of springs 126 in restoring the cylinder to the centered position at which controlvalve 13 is in the Hold position and motor 12 is immobilized.

The driver circuit '32 operates in a similar manner in responseto'termination of a Contract signal on conductor 42'. Through an actionsimilar to that described above, solenoid 28 is momentarily energizedupon deenergizing of solenoid 27'.

i A somewhat simpler driver circuit may be utilized in instances wherethe control signals are received through electricalconductors,generallycontained in a lengthy umbilical cord, rather than through radiosignals. FIG. "2 illustrates a'modification of the invention. adaptedfor umbilical cord control. The electromechanical apparatus 11' which isto be controlled from a remote location by the modified driver circuit32' of FIG. 2' may be similar to that described with reference topreviousembodiments and thus includes a hydraulic motor 12 operatedby'pressurized fluid from a suitable source'16f by'manipulation of anactuator arm 14' of a control valve 13'. Under non-remote controlconditions, actuator lever 14' is operated by pivoting a control lever18' through linkage 1'9 connecting the two levers. To'provide foroptional remote control, a small fluid cylinder-23: defines a portion ofthe linkage 19- between levers 18' and 14" and contains centeringsprings 26' which cause the cylinder to function effectively as arigid-link when control lever 18' is pivoted. Cylinder 23' may beextended for remote control purposes'by energizing a solenoid valve 28"controlled by a solenoid 28" and the cylinder may be caused to contractby energizing an additional solenoid valve 27 having a control solenoid27". Energization of solenoid 28" causes pressurized fluid from a source31' to be transmitted to the rod end of cylinder 23' while energizationof solenoid 27" causes fluid'from source 31" tobe directed to the headend of cylinder 23'. The detailed construction and operation of theabove described fluid system components of the apparatus of FIG. 2 maybe identicalto that of the system 11 previously described with referenceto the first embodiment of the apparatus.

A suitable DC power supply such as a battery 33' has the negative sidegrounded and has a positive side connected by a power conductor 34' withone terminal of each solenoid'27' and28' through the emitter'collectorcircuits of power transistors 61 and 61' respec-' tively. Thussolenoid27" connects with battery 33' through the emitter collector circuit oftransistor 61 and solenoid'28""connects with battery 33' through theemitter collector circuit oftransistor 61 To guard against invertedvoltages, diodes 62 and 62' are disposed between the battery 33' andtransistors 61 and 61' respectively. The other terminals of bothsolenoids 27" and 28" are grounded and each has a protective diode 63connected thereacross in series with resistors 64 and 64' respectivelyfAccordingly solenoid valve 27" or valve 28" may be selectivelyoperatedby biasing transistor 61 or 61' respectively into conduction.

To control the power transistors 61 and 61 in response to signals from aremote location, driver circuit 32' has an Extend signal conductor 66and a Contract signal conductor 66 which, together with a groundpotential conductor 67, extend through an umbilical cord 68 to a remotecontrol unit 69 which may of the apparatus. I

The base of power transistor 61 is connected to Extend signal conductor66 through a resistor 71 and protective diode 72 while the base oftransistor 61 is similarly connected to Contract signal conductor 66through a resistor 71' and diode 72. Remote control unit 69 has a firstnormally open, manually operable switch 74 for selectively connectingExtend signal conductor 66 .to ground conductor 67. Grounding of signalconductor 66 establishes a voltage drop across resistor 71 which biasespower transistor 61 into conduction thereby energizing valve solenoid27". Similarly, the remote control unit 69 has a second normally openmanually operable switch 74 for selectively grounding signal conductor66' to bias power transistor 61 into conduction and thereby energizevalve solenoid 28".

The driver circuit 32 of FIG. 2 as described to this point provides ameans by which hydraulic motor 12 may be selectively caused to extend orcontract by operation of switches 74 and 74' respectively. Ashereinbefore discussed an undesirable delay in response of motor 12 totermination of a control signal may occur in the absence of correctivemeasures. As in the previous instance, the modified driver circuit 32'provides for a brief energization of a solenoid 27" or 28" followingtermination of energization of the other solenoid so that restoration ofcylinder 23 to theintermediate position is assisted by fluid pressurefrom source 31'. g

To perform this function, the signal conductors 66 and 66' are connectedto ground through the emitter collector circuits of a pair of signal enddetector transistors 76 and 76 respectively and through a single diode77. Thus either signal conductor 66 or 66 may be grounded to turn on theassociated power transistor 61 or 61' by biasing the associatedtransistor 76 or 76 into conduction, the'effect being similar to closingof one of the'manually operated switches 74 and 74 at the remote controlunit 69.

The base of transistor 76 connects to the positive side of battery 33through a capacitor 78 and resistor 79 while the base of transistor 76'is similarly connected to the positive side of the battery through besituated at any desired distance from the remainder capacitor 78 andresistor 79'. Extend signal conductor 66 is connected to the junction81' between capacitor 78' and resistor 79 while contract signalconductor 66' is similarly connected to the junction 81 betweencapacitor 78 and resistor 79. Diodes 82 and 82' are connected betweenground and the bases of transistors 76 and 76' respectively.

During the period when both manually operated switches 74 and 74' at theremote control unit are open, capacitors 78 and 78 are charged owning tothe connection-to battery 33' through resistors 79 and 79' respectively.With capacitors 78 and 78' fully charged and switches 74 and 74 opened,no base bias is present at transistor 76 and 76' and both suchtransistors are turned off. Upon closing of switch 74, for example,extend signal conductor 66 is grounded as previously described causingenergization of solenoid 27 by the resultant conduction through powertransistor 61. This closing of switch 74 also provides adischarge pathfor capacitor 78' owing to the connection between extend signalconductor 66 and junction point 81'. When switch 74 is subsequentlyopened to de-energize solenoid 27", the ground connection to terminalpoint 81 is removed and capacitor 78 begins to recharge. During theperiod that capacitor 81' is in the process of recharging, transistor76' becomes conductive. Conduction through transistor 76'.is brief asthe base bias thereat exists only while capacitor 78' is charging andends when a steady charge condition is reestablished in the capacitor.During this brief period at which transistor 76' conducts, powertransistor 61 is also biased into conduction to briefly energizesolenoid 28". This momentarily operates valve 28" to cause pressurizedfluid from source 31 to accelerate the action of springs 26' in cylinder23 in restoring control valve 13 to the Hold position at which motor 12is immobilized.

Closing of switch 74' at remote control unit 69 and the eventualreopening of switch 74' produces an essentially, similar effect. Whenswitch 74 is reopened, solenoid 28" is de-energized as previouslydescribed. The reopening of switch74' also causes capacitor 78 torecharge and to turn on transistor 76 during the brief rechargingperiod. During the period that transistor 76 is conductive, solenoid27'-" is energized enabling the force of fluid from source 31' toaccelerate restoration of control valve 13' to the Hold position.

Thus the circuit depicted in FIG. 2 differs from that of FIG. 1 in thatno transistors are conductive in the absence of a control signal.Control signals are generated by the grounding of the signal conductors66 and 66 rather than the application of positive voltage thereto.Capacitors .78 'and 78' generate a brief inverse mode of valveoperation, following termination of a control signal, while chargingrather than while discharging. Thus many variations are possible withinthe scope of the invention and it is not intended to limit the inventionexcept as defined in the following claims.

What is claimed is:

1. A circuit for controlling electrically actuated mechanism in responseto signals of selectively variable duration from a remote location, saidmechanism having a first terminal at which electrical voltage is changedto provide a forward mode of operation for a selected period and havinga second terminal at which electrical voltage is changed to provide areversed mode of operation for a selected period, comprising:

a first signal conductor for receiving signals from said 9 a secondsignal conductor for receiving signals from said remote locationforinitiating operation of said mechanism in said reversed mode thereof,a means for changing voltage at said second terminal in response-to asignal on said 'secondsignal conductor, and for maintaining said voltagechange for the duration of said signal, and means for responding totermination of each signal .on said first signalfconductor by brieflychanging thevoltage at-saidsecond terminal to momentarily V tocause saidcylinder-to shiftsaid control valve actuatoperate said mechanis'min saidreversed rn'r' de'and responding tottermin ation of each signal on isecond signalconductor by briefly changing the voltage of said firstterminal to momentarily operate saidmechanism in saidforward mode.

i 2. The combination defined in claim lvwherein said means for changingvoltage at said first terminal and said means for changing voltageatsaid second terminal comprise transistors which changestate betweenconductive and nonconductive conditions in response to saidforwardlmode' and reverse mode signals at said first and second signalconductors respectively and wherein said means responding; to"termination of said signals comprises capacitivemeans which changescharge condition in response to each of said signals'causing a change ofstate of one'of saidtransistors and which comprising:

briefly changes the state of the other of said transistors ingtermination of eachof said signals.

3. The combination defined in claim 2 further cornprising a DC powerconductor and wherein said first terminal is connected to saidpowerconductor through the emitter collector circuit of "afirst of: saidtransistors and wherein said second terminal is'connected to said powerconductor through the emittcrcollector circuit of the second of saidtransistors; further comprising means connected betweenthe base of said'first transistor and saidfirst signal conductor for biasing said Ifirsttransistor intoyconduction .inresponse to each forward mode signalat said 'first signal conductor and means connected between the' base ofsaid second transistor and said second signal conductor for biasing saidsecond transistor into conduction in response to each reversed mode.signal atsaidsecond conductor,

said capacitive means momentarily biasing said second transistor toconduction upon "termination of each of said forward mode signals atsaid first signal conductor and momentarily biasing said firsttransistor to conduction upon termination of each of said reversed modesignals at said second signal conductor. a

4; The combination defined in claim 1 whereinsaid electrically actuatedmechanism comprises an extensible andcontractible fluid motor, a controlvalve for said motor having actuator means movable between threepositions including a position at which said motor is caused to extendand a position at which said motor is caused to contract and a positionat which said motor is immobilized, a fluid cylinder connected to saidcontrol valve actuating means and being extensible and pon reverting tothe original charge condition followcontractible to shift said actuatingmeans between said at which said actuator lever immobilizes said fluidmotor, and" wherein said first terminal controls an electricallyoperated valve for directing fluidjto said cylinder ing means to'themotor extendin'gpositionthereof and wherein saidsecond terminalcontrolsa second electrically operated valvefor'directing'fluid to saidcylinder tocause said cylinder to shift'said control valve actuatingmeans to 'themotor contracting positionthereof.

5. A driver circuit for an electrically controlled motorhaving afirstterminal which is electrically energizedvto cause motor operation in aforwar'd direction and having a second terrninal'which is electricallyenergizejd to cause motor operation in a reverse direction,

a power'conductor, v

a first transistor havin'gan emitter collector circuit coupledbetweensaid power conductor and said first terminal and having a base, i

a second transistor having aniemitter collector circuitcoupled betweensaid power conductor and said second terminal andhaving a base, I v

first signal input means for-receiving first signal s vof selectivelyvariable duration from a remote location and forbiasing'said base ofsaidfirst transistor to provide for conduction therethrough for the durationof each of said first signals from a remote location, a

second signal input means for receiving second signals of selectivelyvariableduration from said remote location and for biasing said base ofsaid second transistor to provide for conduction therethrough for theduration of veach of said second signals from said remote location,

first capacitive means coupled between said first signal 'input meansandsaid base of said second transistor for'changing charge state inresponse to 7 each first signal atsaid first inputlmeans and for biasingsaid "second transistor into conduction while reverting to the originalcharge state follow ing termination of each of said first signals atsaid first inputmeansandw v H W second capacitive means coupled betweensaid second signal input means and said base of said first transistorfor changing charge state in responseto each second signal at saidsecond input means and for biasing said first transistor into conductioniwhile reverting to the original charge state following termination ofeach of said second signals at said second input means.

6. A driver circuit as defined in claim 5 further comprising a normallyconductive third transistor having a base and being coupled to saidpower conductor for providing base bias to said first transistor to holdsaid first transistor nonconductive in the absence of one of said firstsignals at said first signal input means, a voltage divider connected tosaid power conductor for comprises a capacitor connected between saidthird transistor base andsaid second signal input means whereby each ofsaidsecond signals on said second signal input means chargessaid'capacitor and the sub sequent discharge of said capacitorfollowing'termination of each of said second signals momentarily renderssaid third transistor nonconductive to cause momentary conductionthrough saidjfirst transistor.

7. A driver circuit as definedin claim 6 further comprising a normallyconductive fourth transistor having a base and being coupled to saidpower conductor for providing base bias to said second transitor to holdsaid second transistor nonconductive in the absence of one of saidsecond signals at said second signal input means, a second voltagedivider connected to said power conductor for providing base bias tosaid fourth transistor for holding said fourth transistor in saidnormally conductive condition thereof, said first capacitive meanscomprising a second capacitor connected between said fourth transistorbase and said first signal input means whereby each of said firstsignals on said first input means charges said second capacitor and thesubsequent discharge of said second capacitor following termination ofeach of said first signals momentarily renders said fourth transistornonconductive to cause momentary conduction through said secondtransistor.

8. A driver circuit as defined in claim wherein said first and secondtransistors each have a resistor connected to the base thereof andwherein said first and second signal input means have remotely situatedswitches for selectively connecting the base resistors of said first andsecondtransistors to a second conductor having a potential differingfrom that of said power conductor whereby either of said first andsecond transistors may be caused to conduct by operation of said remoteswitches, further comprising a normally nonconductive third transistorhaving a base and having an emitter collector circuit connected betweensaid second conductor and said base of said first transistor throughsaid resistor thereat for providing an alternate means for biasing saidfirst transistor into conduction, and wherein said second capacitivemeans comprises a capacitor having one side connected to said base ofsaid third transistor and having the other side connected to said powerconductor and to said second signal input means whereby said capacitoris discharged by closing of said remote switch associated with saidsecond signal input means and recharges upon reopening of said switchbriefly biasing said third transistor into a conductive condition duringthe recharging period.

9. A driver circuit as defined in claim 8 further comprising a normallynonconductive fourth transistor having a base and having an emittercollector circuit connected between said ground conductor and said baseof said second transistor through said resistor thereat for providing analternate means for biasing said second transistor into conduction, andwherein said first capacitive means further comprising an additionalcapacitor having one side connected to said base of said fourthtransistor and having the other side connected to said power supplyconductor and to said first signal input means.

1. A circuit for controlling electrically actuated mechanism in responseto signals of selectively variable duration from a remote location, saidmechanism having a first terminal at which electrical voltage is changedto provide a forward mode of operation for a selected period and havinga second terminal at which electrical voltage is changed to provide areversed mode of operation for a selected period, comprising: a firstsignal conductor for receiving signals from said remote location forinitiating operation of said mechanism in said forward mode thereof,means for changing voltage at said first terminal in response to asignal on said first signal conductor and for maintaining said voltagechange for the duration of said signal, a second signal conductor forreceiving signals from said remote location for initiating operation ofsaid mechanism in said reversed mode thereof, means for changing voltageat said second terminal in response to a signal on said second signalconductor, and for maintaining said voltage change for the duration ofsaid signal, and means for responding to termination of each signal onsaid first signal conductor by briefly changing the voltage at saidsecond terminal to momentarily operate said mechanism in said reversedmode and responding to termination of each signal on said second signalconductor by briefly changing the voltage of said first terminal tomomentarily operate said mechanism in said forward mode.
 2. Thecombination defined in claim 1 wherein said means for changing voltageat said first terminal and said means for changing voltage at saidsecond terminal comprise transistors which change state betweenconductive and nonconductive conditions in response to said forward modeand reverse mode signals at said first and second signal conductorsrespectively and wherein said means responding to termination of saidsignals comprises capacitive means which changes charge condition inresponse to each of said signals causing a change of state of one ofsaid transistors and which briefly changes the state of the other ofsaid transistors upon reverting to the original charge conditionfollowing termination of each of said signals.
 3. The combinationdefined in claim 2 further comprising a DC power conductor and whereinsaid first terminal is connected to said power conductor through theemitter collector circuit of a first of said transistors and whereinsaid second terminal is connected to said power conductor through theemitter collector circuit of the second of said transistors, furthercomprising means connected between the base of said first transistor andsaid first signal conductor for biasing said first transistor intoconduction in response to each forward mode signal at said first signalconductor and means connected between the base of said second transistorand said second signal conductor for biasing said second transistor intoconduction in response to each reversed mode signal at said secondconductor, said capacitive means momentarily biasing said secondtransistor to conduction upon termination of each of said forward modesignals at said first signal conductor and momentarily biasing saidfirst transistor to conduction upon termination of each of said reversedmode signals at said second signal conductor.
 4. The combination definedin claim 1 wherein said electrically actuated mechanism comprises anextensible and contractible fluid motor, a control valve for said motorhaving actuator means movable between three positions including aposition at which said motor is caused to extend and a position at whichsaid motor is caused to contract and a position at which said motor isimmobilized, a fluid cylinder connected to said control valVe actuatingmeans and being extensible and contractible to shift said actuatingmeans between said three positions thereof and having resilient meansacting thereon tending to urge said cylinder to the position at whichsaid actuator lever immobilizes said fluid motor, and wherein said firstterminal controls an electrically operated valve for directing fluid tosaid cylinder to cause said cylinder to shift said control valveactuating means to the motor extending position thereof and wherein saidsecond terminal controls a second electrically operated valve fordirecting fluid to said cylinder to cause said cylinder to shift saidcontrol valve actuating means to the motor contracting position thereof.5. A driver circuit for an electrically controlled motor having a firstterminal which is electrically energized to cause motor operation in aforward direction and having a second terminal which is electricallyenergized to cause motor operation in a reverse direction, comprising: apower conductor, a first transistor having an emitter collector circuitcoupled between said power conductor and said first terminal and havinga base, a second transistor having an emitter collector circuit coupledbetween said power conductor and said second terminal and having a base,first signal input means for receiving first signals of selectivelyvariable duration from a remote location and for biasing said base ofsaid first transistor to provide for conduction therethrough for theduration of each of said first signals from a remote location, secondsignal input means for receiving second signals of selectively variableduration from said remote location and for biasing said base of saidsecond transistor to provide for conduction therethrough for theduration of each of said second signals from said remote location, firstcapacitive means coupled between said first signal input means and saidbase of said second transistor for changing charge state in response toeach first signal at said first input means and for biasing said secondtransistor into conduction while reverting to the original charge statefollowing termination of each of said first signals at said first inputmeans, and second capacitive means coupled between said second signalinput means and said base of said first transistor for changing chargestate in response to each second signal at said second input means andfor biasing said first transistor into conduction while reverting to theoriginal charge state following termination of each of said secondsignals at said second input means.
 6. A driver circuit as defined inclaim 5 further comprising a normally conductive third transistor havinga base and being coupled to said power conductor for providing base biasto said first transistor to hold said first transistor nonconductive inthe absence of one of said first signals at said first signal inputmeans, a voltage divider connected to said power conductor for providingbase bias to said third transistor for holding said third transistor insaid normally conductive condition thereof, and wherein said secondcapacitive means comprises a capacitor connected between said thirdtransistor base and said second signal input means whereby each of saidsecond signals on said second signal input means charges said capacitorand the subsequent discharge of said capacitor following termination ofeach of said second signals momentarily renders said third transistornonconductive to cause momentary conduction through said firsttransistor.
 7. A driver circuit as defined in claim 6 further comprisinga normally conductive fourth transistor having a base and being coupledto said power conductor for providing base bias to said second transitorto hold said second transistor nonconductive in the absence of one ofsaid second signals at said second signal input means, a second voltagedivider connected to said power conductor for providing base bias tosaid fourth transistor for holding said fourth trAnsistor in saidnormally conductive condition thereof, said first capacitive meanscomprising a second capacitor connected between said fourth transistorbase and said first signal input means whereby each of said firstsignals on said first input means charges said second capacitor and thesubsequent discharge of said second capacitor following termination ofeach of said first signals momentarily renders said fourth transistornonconductive to cause momentary conduction through said secondtransistor.
 8. A driver circuit as defined in claim 5 wherein said firstand second transistors each have a resistor connected to the basethereof and wherein said first and second signal input means haveremotely situated switches for selectively connecting the base resistorsof said first and second transistors to a second conductor having apotential differing from that of said power conductor whereby either ofsaid first and second transistors may be caused to conduct by operationof said remote switches, further comprising a normally nonconductivethird transistor having a base and having an emitter collector circuitconnected between said second conductor and said base of said firsttransistor through said resistor thereat for providing an alternatemeans for biasing said first transistor into conduction, and whereinsaid second capacitive means comprises a capacitor having one sideconnected to said base of said third transistor and having the otherside connected to said power conductor and to said second signal inputmeans whereby said capacitor is discharged by closing of said remoteswitch associated with said second signal input means and recharges uponreopening of said switch briefly biasing said third transistor into aconductive condition during the recharging period.
 9. A driver circuitas defined in claim 8 further comprising a normally nonconductive fourthtransistor having a base and having an emitter collector circuitconnected between said ground conductor and said base of said secondtransistor through said resistor thereat for providing an alternatemeans for biasing said second transistor into conduction, and whereinsaid first capacitive means further comprising an additional capacitorhaving one side connected to said base of said fourth transistor andhaving the other side connected to said power supply conductor and tosaid first signal input means.